Kenneth D. Blehm

Characterization of Particleboard Aerosol — Size Distribution and Formaldehyde Content

Health hazards unique to particleboard include the generation of urea-formaldehyde resin bound in wood aerosol and release of formaldehyde gas that can be inhaled by the worker. A particleboard aerosol was generated by a sanding process and collected under laboratory conditions that determined the particle size distribution and formaldehyde content. Three side-by-side Marple 296 personal cascade impactors with midget impingers attached downstream collected particleboard aerosol and gaseous formaldehyde for ten sample runs. Gravimetric analysis quantified the collected aerosol mass, and chromotropic acid/spectrophotometric analytical methods were employed for formaldehyde content in particleboard aerosol and gaseous formaldehyde liberated from sanded particleboard. Significant variations (p less than .005) were observed for the particleboard mass and gaseous formaldehyde collected between sample runs. No significant differences (alpha = .05) were observed for the aerosol size distribution determined and formaldehyde content in particleboard aerosol per unit mass for sampling trials. The overall MMAD of particleboard aerosol was 8.26 microns AED with a sigma g of 2.01. A predictive model was derived for determining the expected formaldehyde content (microgram) by particleboard aerosol mass (mg) collected and particulate size (micron AED).

Infrared Thermometry in the Measurement of Heat Stress in Firefighters Wearing Protective Clothing

Abstract This study investigated the performance of a new infrared-sensing thermometer in the determination of heat stress in firefighters performing moderate exercise in two protective clothing ensembles. All existing consensus standards approach the topic of heat stress monitoring and prevention. These standards are designed to keep the core body temperature of workers below 38°C. Direct measurement of rectal temperature is inconvenient and impractical, so surrogate measures of environmental heat have been widely accepted. Surrogate measures are poor predictors of heat stress in situations where protective clothing interferes with the bodys means of losing heat. In these situations, direct measurement of the bodys response to heat is desirable. Previous investigation had shown the effectiveness of infrared thermometry in a surgical setting, but no research had been done in the area of worker monitoring. Eight hazardous materials-trained firefighters exercised on a stair machine while wearing gym cloth...

Controlling Airborne Lead in Indoor Firing Ranges

Abstract Industrial hygiene investigations of indoor firing ranges have revealed adverse health effects in range personnel from lead exposure. The most significant exposure source has been airborne lead generated during weapon firing. Dilution ventilation has been recommended as a way to control lead exposure in indoor ranges by the National Institute for Occupational Safety and Health, the American Conference of Governmental Industrial Hygienists, and the National Rifle Association. This research evaluated the effectiveness of using source capture local exhaust ventilation in conjunction with dilution ventilation as a means of controlling the lead dusts and fumes. Air monitoring was conducted to determine effectiveness of control techniques for reducing airborne lead concentrations. The first trial was performed during firing of copper-jacketed bullets and using dilution ventilation. The second trial monitored airborne lead while firing lead bullets and utilizing dilution ventilation. The third trial eva...

An Evaluation of Benzene in the Presence of Gasoline by Active and Passive Sampling Methods

Abstract This research project examined the capability of both the active and passive methods to evaluate the amount of benzene vapor in an environment composed of a complex mixture of competing organic vapors (gasoline). Activated charcoal tubes and three brands of passive organic vapor monitors (3M 3520, SKC Solid Sorbent Badge, and MSA VaporgardTM) were exposed to four concentration levels of benzene in the presence of gasoline, and all results were evaluated against the NIOSH acceptance criteria for sampling and analytical methods. Each type of sampler was then compared to each of the other tested samplers to determine the overall similarity of the results as determined by the different devices. The samplers were also subjected to a benzene environment without gasoline to establish baseline response criteria for comparative purposes. The test results indicated that three of the four methods examined met the NIOSH criteria (ACT, 3M, and SKC). The fourth method (MSA) failed due to significant benzene le...

A Comparison of Tape Sampling and Microvacuum Procedures for the Collection of Surface Glass Fiber Contamination

Abstract Currently, few published methods exist for assessing surface contamination of asbestos and other fibers. Several surface sampling procedures have been employed: the wipe sampling method, the tape sampling method, and a more recent procedure commonly known as the microvacuum or microvacing procedure. Wipe sampling is not appropriate for sampling fibers on a surface, and limited studies have been reported which describe the procedure and validation of the tape sampling method or the microvacing procedure with respect to quantitative recovery, repeatability, or methodology. Therefore, this laboratory study evaluated the relative efficiency and reproducibility of two tape sampling and two microvacing procedures in use at a large multibuilding government facility for assessing surface contamination of fibrous materials, and quantitatively compared the most efficient and reproducible tape sampling method with the most efficient and reproducible microvacing procedure. The one-pat and three-pat tape samp...

Characterization of Lead Fume Exposure during Gas Metal Arc Welding on Carbon Steel

Abstract This study was undertaken to determine if the welding fume generated during gas metal arc welding on carbon steel is a significant source of lead exposure to welders. Lead and total fume concentrations were determined for gas metal arc welding on three types of carbon steel. Lead concentrations between base metals were compared, and an attempt was made to generate a predictive model for lead concentration based on total welding fume. Total fume concentrations ranged from 10 to 110 mg/m3 with a geometric mean of 31.6 mg/m3. Lead concentrations ranged from 1.0 to 17.6 μg/m3 with a geometric mean of 4.8 μg/m3. These lead concentrations were well below the Occupational Safety and Health Administrations permissible exposure level of 50 μg/m3. The 1018 steel produced significantly higher lead concentrations compared to the other base metals. It was not possible to generate a strong predictive model for lead concentration based on total fume. This study indicated that the lead concentrations in the wel...

A predictive model for determining asbestos concentrations for fibers less than five micrometers in length

The controversy of whether small asbestos fibers are biologically significant has not been resolved. The present standard method for evaluating asbestos fiber concentrations in workroom air excludes fibers less than 5 micron long even though it has been shown that small fiber concentrations dominate in a dust cloud. This research project was conducted to develop a mathematical model whereby one could predict small (less than 5 micron length) asbestos fiber concentration based on the fiber count concentration determined by phase contrast microscope analysis. Dry chrysotile asbestos was aerosolized into a chamber and sampled by membrane filtration. Segments from each filter were analyzed by both the NIOSH technique using phase contrast microscopy (PCM) and scanning electron microscopy (SEM) at 2000 X for fiber concentrations. A linear relationship was found to exist between the natural logarithm of the SEM-determined concentration and the natural logarithm of the PCM-determined concentration (r = 0.852). Using these data, a mathematical model was developed to predict SEM concentrations based on PCM counts. This model may have application in retrospective epidemiological studies for estimating small fiber exposure levels to determine if small fibers play a role in disease production. The greatest utility would be in those retrospective studies where the only exposure information available is based on PCM counts.

“Ducting” as a Pneumatic Noise Control Technique

This study was designed to develop “ducting” techniques for pneumatic noise control and to determine their feasibilities under field conditions. Pneumatic noise was generated under laboratory conditions and characterized by one-third octave-band measurements. Then two forms of ducting were evaluated for their effectiveness in noise control. Static pressures were measured pre- and post-control to evaluate induced back pressure. Variations of the ducting techniques then were applied to several machines under actual work conditions. Analyses of the laboratory measurements indicated a substantial decrease in sound pressure level between pre-control and post-control noise measurements. A slight increase in static pressure also was indicated. Analyses of pre-control and post-control noise measurements during field validation trials showed typical decreases of 10 to 29 dB(A). Therefore, it was demonstrated that ducting effectively reduced pneumatic noise in the work environment and can be utilized as an alternat...

A Comparison of Two Ozone Sampling Methods

A study was conducted to compare the alkaline potassium iodide (AKI) impinger method versus a direct-reading chemiluminescent monitor for determining ozone concentrations. Comparisons were made in both a controlled laboratory situation and in the field during MIG welding. Laboratory results indicated that the accuracy of the AKI procedure is affected by sample size. In the field, AKI impinger samples seemed to give very low estimations of the true ozone concentration. The direct-reading chemiluminescent monitor performed excellently in both the laboratory and field, and exhibited its merit as an industrial hygiene field instrument.

A Predictive Model for Vapor Concentration in a Nose-Only Inhalation Chamber

A unique nose-only inhalation chamber was designed and constructed to deliver uniform concentrations of gas, vapor, and aerosol contaminants to mice. This research investigated the fluid dynamics of a vaporous contaminant in the vertical flow chamber. The vapor was introduced by allowing the liquid phase of the contaminant to evaporate freely into the chamber interior. A contaminant mass transfer model was developed to predict concentrations generated by the system. The mathematical model of the system used clean airflow, liquid surface area, thickness of the stagnant air layer covering the liquid, system pressure, contaminant diffusion coefficient, and contaminant vapor pressure to compute the vapor concentration delivered to exposure ports. The equation was verified by placing various containers of methyl isobutyl ketone in the chamber and determining with a photospectrometer the resulting equilibrium concentrations. Vapor pressure, diffusion coefficient, and system pressure were held constant while airflow, surface area, and stagnant air layer thickness were varied systematically within the chamber. The resulting empirical data points were compared to the curves predicted by the theoretical model. Empirical concentrations fell within 0 to 48% of the theoretical values, showing that the equation can be used to choose values for airflow, surface area, and stagnant air layer thickness that will result in chamber concentrations in close proximity to the target concentration. If an exact concentration is essential, parameters may be individually adjusted to converge on the target concentration.